1. Technical Field
This invention relates to an electrical alarm circuit. In particular, an alarm circuit for detecting the opening of either of two doors on a semi trailer.
2. Background Art
The independent trucker has an additional burden placed on him by his customers which is the security of the customer's goods. Because of the nature of the trucking business, it is impractical for the independent driver to provide around-the-clock security for his cargo during stopovers, rest periods, lunch breaks, and the like. It is therefore necessary to provide some deterrent method which can be controlled by the truck driver. What is needed is a simple, low cost, tamper alarm which is designed specifically for use in a semi trailer and is easy to operate and install.
The art is filled with burgular alarms tailored to fulfil a specific need. FITCHETT, U.S. Pat. No. 4,118,692, teaches an alarm device incorporated into the closure hardware of a standard lockable attache type handbag. If the bag is opened by other than authorized means, the alarm sounds.
A hinge mounted micro switch as taught in PETERSON, U.S. Pat. No. 3,715,537, electrically connected to an alarm circuit might satisfy the need, however retrofitting a semi trailer with the hinge mounted micro switch would be both costly and sometimes complicated.
Accordingly, it is an object of this invention to provide an alarm circuit for detecting the opening of either of two semi trailer doors which is both cost effective and easy to install.
A second object of this invention is to provide an alarm means which is simple to operate yet effective in deterring a possible cargo theft.